<template>
  <div class="pagination">
    <button @click="changeGoods(pageNo-1)" :disabled="pageNo === 1">上一页</button>
    <button  @click="changeGoods(1)" v-show="startEnd.start !== 1">1</button>
    <span v-show="startEnd.start > 2">···</span>

    <!-- <button>{{ startEnd.start }}</button>
    <button>7</button>
    <button class="active">{{ pageNo }}</button>
    <button>9</button>
    <button>{{ startEnd.end }}</button> -->
    <button  @click="changeGoods(startEnd.start + index)" :class="{active:startEnd.start + index === pageNo}" v-for="(n,index) in (startEnd.end - startEnd.start + 1)" :key="index">{{ startEnd.start + index }}</button>

    <span v-show="startEnd.end < pageTotal-1">···</span>
    <button @click="changeGoods(pageTotal)" v-show="startEnd.end !==pageTotal">{{ pageTotal }}</button>
    <button @click="changeGoods(pageNo + 1)" :disabled="pageNo === pageTotal">下一页</button>

    <span>共 {{ total }} 条</span>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:{
    total:{
        required:true
    },
    pageSize:{
        type:Number,
        required:true
    },
    pageNo:{
        type:Number,
        required:true
    },
    continues:{
        type:Number,
        required:true
    },
    changeGoods:{
      type:Function,
      required:true
    }
  },
  computed:{
    pageTotal(){
        return Math.ceil(this.total/this.pageSize)
    },
    startEnd(){
        let {pageSize,pageNo,total,continues,pageTotal} = this
        let start = 0
        let end = 0
        
        if(continues > pageTotal){
            start = 1,
            end = pageTotal
        }else{
            start = pageNo - (continues - 1)/2
            end = pageNo + (continues - 1)/2
            if(start < 1){
                start = 1
                end = continues
            }
            if(end > pageTotal){
                start = pageTotal - continues + 1
                end = pageTotal
            }
        }
        return {
            start,
            end
        }
    }
  }
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: gray;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #c81623;
      color: #fff;
    }
  }

  span {
    display: inline-block;
    line-height: 28px;
    font-size: 14px;
    color: gray;
    vertical-align: middle;
  }
}
</style>